The present invention relates to a radiation focal position detecting method, a radiation detecting apparatus and a radiation tomographic imaging apparatus, and more specifically to a technology which detects a positional displacement of a radiation focal point of a radiation source in high resolution.
In a radiation tomographic imaging apparatus having a multi-detector, such as a multi-slice X-ray CT apparatus or the like, the accuracy of position of a radiation focal point of a radiation source is very important in maintaining an acquired image in high quality. A position error in the radiation focal point may affect the geometry of a data acquisition system, thus resulting in the occurrence of serious artifacts in a high resolution region of the acquired image. In a recent radiation detecting apparatus in particular, a two-dimensional collimator having collimator plates arranged in channel and slice directions are often used to reduce scattered radiation incident to each detecting element. In this case, the adverse effect due to the position error in the radiation focal point becomes more serious.
The movement of the radiation focal point due to a change in the temperature of the radiation source has heretofore been present as almost inevitable. As its countermeasures, the position of the radiation focal point and the amount of movement thereof are detected based on, for example, a reference channel of a radiation detector. That is, profiles of radiation detection signals in a reference detecting element group, and the correction of projection data and control on radiation in a radiation direction have been conducted based on the so-detected information. See, for example, Japanese Patent Laid-Open No. Hei 6-169914, FIGS. 8 through 13, etc., and Japanese Patent Laid-Open No. Hei 8-280659, FIG. 10, etc.
The detecting elements and the collimator plates have however been miniaturized in recent years, and the general related art method as described above has difficulty detecting the position of the radiation focal point and the amount of movement thereof with sufficient resolution.
With such circumstances, there has been a demand for a technology capable of detecting a positional displacement of the radiation focal point of the radiation source in high resolution.